1. Field of Invention
The present invention relates generally to multi-projector display systems. More particularly, the present invention relates to accurate calibration of the system during registration of the each of the multiple projectors.
2. Background
With an ever growing desire to see more information with better quality, large-screen displays have become quite popular. Increasing screen resolutions and sizes are continually emerging and made available in televisions, computer monitors, and other video devices. Until recently, large screen displays were typically too costly, physically unwieldy, or simply unavailable. Video projectors provided one solution, enabling a wide range of communication and entertainment functions by offering a significantly greater display area relatively inexpensively. These devices have found application in conference rooms for presentations, home theaters, classroom training, and advertising billboard displays.
Similar to other video device technologies, video projectors continue to advance their displayable pixel resolution and light output. Today commodity projectors are brighter, offer better quality, and are often less expensive than those of prior years. Highly portable projectors (in both weight and size) are also becoming readily available. No longer do commodity projectors remain constrained to dimly lit rooms with well prepared display surfaces. A video projector's small physical size relative to its large projection output therefore remains appealing.
Even with these improvements, however, it is still difficult or impossible for a single commodity projector to achieve very high resolutions, project over vast areas, or create bright projections on very bright surface areas (for example, near day lit windows). Applications demanding such display qualities, however, are becoming more desirable. The benefits of increased resolution, brightness, and larger display surface area have proven useful for reaching larger audiences and providing full-scale life-sized immersive environments. Unfortunately, construction of such large displays is complex and costly.
One common technique, such as grouping multiple projectors together and tiling their projection output to produce large screen displays of any desired size, presents challenging problems with registration (that is, alignment of projector pixels). Color and luminosity variance across separate devices and even within a given device is difficult to correct. Minor shape or geometric inconsistencies of the display surface can also hinder adequate results. Projector lumens, or light output, may not be adequate for brighter locations. Synchronizing content delivery to the individual components forming in the larger display are additional hurdles to solve. Some of these problems apply to single-projector displays as well.
Solutions to some of these system problems take many forms. Many require precise pixel and color alignment using manual methods that require physical adjustment of the projector placement. If the output pixels from one projector are not close enough to those from another projector, a visible gap may occur between the projections on the composite display. Likewise, overlapping pixels across projectors produce bright seams that are also objectionable. High-end projectors with specialized lens optics or edge blending/blurring filters may be available to reduce some of these problems, but are far from optimal.
Specialized projectors and mounting hardware, measurement tools, and tedious calibration methods are additional requirements that add to the resource costs and complexities of physical projector alignment which can become too demanding for the average user. The advanced skills and time requirements are more than most will invest. In many configurations, physical alignment may even be impossible using projectors with limited optic pathways, or with even slightly irregular display surfaces. When changes are necessary to replace failed lamps, the calibration methods often need repeating.
What is needed is a system that provides an easy calibration and playback mechanism offering the typical user an automated method to create a composite display from one or more commodity projectors, even in the presence of high ambient light levels. This method should offer a relatively quick one-time calibration function to be performed once after casual projector placement or changes.